A generally known cushion using air cells having air cells provided so as to be arranged side by side with each along a seating surface, the air cells respectively consist of air bags which extend upward, a flexible base member configured so as to extend along the seating surface and support lower side of each of the air cells, an air passage for letting the interiors of the air cells communicate mutually. When a person sits down the air cells, air pressures in each of the air cells become equal mutually, and the pressure generated on the buttock of the seated person disperses.
With regard to the said cushion, air having a predetermined pressure is introduced into the air cells, and after the person is sat down on the air cells, air is bled from the air cells. With regard to the most collapsed one of the air cells, if an amount of air is controlled so that the upper end side of the air cell does not contact to the base member side, the pressure generated on the buttock of the seated person disperses effectively. However, it is difficult to confirm the state of collapse of the said air cells in the state in which the person is seated.
Therefore, a generally known cushion having air cells which consist of air bags extending upward, a first contact provided in the air bag of the air cell and attached to the upper end surface of the air bag, a second contact provided in the air cell and attached to the lower end side of the air bag, a judging portion provided outside the air cell, the judging portion which is connected with each contact and which judges whether the contacts connect to each other. When the upper side and the lower side of the air bag become nearer than a predetermined distance, the first contact and the second contact connect to each other, and the cushion detects that the upper side and the lower side of the air bag are nearer than the predetermined distance.
Patent Document 1: Japanese Patent publication 06-510436
Patent Document 2: U.S. Pat. No. 6,943,694